1. Field of the Invention
The present invention is directed to an acoustic wave generator of the type having a deformable application cushion and an acoustic wave source within a housing, defining a volume therebetween filled with acoustic propagation medium.
2. Description of the Prior Art and Related Application
A pressure pulse generator is disclosed in co-pending U.S. application Ser. No. 07/761,392, now U.S. Pat. No. 5,207,215, filed Sep. 18, 1991, (Rattner et al), assigned to the same Assignee (Siemens AG) as the present application, wherein the volume containing the acoustic propagation medium, defined between a flexible bellows forming an application cushion and the shockwave source is divided by a wall into two sub-volumes. A first of these sub-volumes is situated between the wall and the pressure pulse source, and is in fluid communication with a reservoir for the liquid acoustic propagation medium via two main lines, so that the acoustic propagation medium contained in the first sub-volume can be circulated.
Pressure pulse generators of this type are used, for example, in medicine for the purpose of treating stone pathologies (lithotripsy), for treating tumors and for treating bone pathologies (osteorestoration). Such pressure pulse sources can also be used for non-medical purpose. The pressure pulse source within the pressure pulse generator can be of the type used to generate shockwaves, or may be of the type to generate diagnostic ultrasound, for example for ultrasound imaging, or for generating therapeutic ultrasound, for example, for treating hyperthermia. The pressure pulse generator may also be suit for generating pressure pulses for materials testing or other purposes. In any case, the generator is acoustically coupled to the subject to be charged with acoustic waves by means of an application cushion, and the subject and the generator are aligned relative to each other so that the acoustic waves pass through the region of the subject which is intended to be acoustically irradiated.
In pressure pulse generators of this type, the separation of the space between the pressure pulse source and the application cushion into two sub-volumes permits the quantity of acoustic propagation medium contained in the second sub-volume, situated between the application cushion and the dividing wall, to be varied for the purpose of acoustically coupling and uncoupling the generator to or from the subject. Upon delivery of acoustic propagation medium to the second sub-volume, the application cushion is forced against the surface of the subject under the influence of the liquid pressure. When the acoustic propagation medium is removed from the second sub-volume, the application cushion falls away from the surface of the subject. Independently thereof, the acoustic propagation medium in the first sub-volume can, for example, be circulated through a cooling system for the purpose of cooling the pressure pulse source, and can be brought to a pressure which can assist in the operation of the source for generating acoustic waves, for example, to influence the movement of the electrically conductive membrane relative to the coil if an electrodynamic pressure pulse source is used. A reservoir and a fluid circulator are required both for the acoustic propagation medium contained in the first sub-volume and in the second sub-volume. This requires known pressure pulse generators of this type to be constructed in a relative complicated manner, and such devices are correspondingly expensive. Moreover, this known type of generator occupies a relatively large space.